A received ATM layer OAM cell processing apparatus for processing in real time a fault management cell among ATM layer OAM cells of F4/F5 levels applied to a user network interface and a network node interface and performing CRC-10 and CRC-32 operations with respect to the other ATM layer OAM cells such as activation/deactivation cells, a resource management cell, a system management cell and a meta signaling cell, not processed in real time. Further, the received ATM layer OAM cell processing apparatus processes in real time a performance management cell among the ATM layer OAM cells of F4/F5 levels applied to the user network interface and network node interface. Therefore, the received ATM layer OAM cell processing apparatus can accumulate in real time performance information such as the total number of received performance management cell blocks, the number of received error cell blocks, the number of received excessive errored cell blocks, the number of lost cells, the number of misinserted cells, the number of discarded cells, the number of tagged cells and the total number of received cells with respect to a specified ATM virtual connection, thereby measuring the service quality and network parameter.